Added Glenn Block's ETagHandler

src/WebApiContrib/MessageHandlers/ETagHandler.cs

@@ -0,0 +1,89 @@
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Linq;
+using System.Net.Http;
+using System.Net.Http.Headers;
+using System.Threading;
+using System.Threading.Tasks;
+using WebApiContrib.ResponseMessages;
+
+namespace WebApiContrib.MessageHandlers
+{
+    // Applied from http://codepaste.net/4w6c6i - by Glenn Block
+    public class ETagHandler : DelegatingHandler
+    {
+        public static ConcurrentDictionary<string, EntityTagHeaderValue> ETagCache = new ConcurrentDictionary<string, EntityTagHeaderValue>();
+
+        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
+        {
+            if (request.Method == HttpMethod.Get)
+            {
+                // should we ignore trailing slash
+                var resource = request.RequestUri.ToString();
+
+                ICollection<EntityTagHeaderValue> etags = request.Headers.IfNoneMatch;
+                // compare the Etag with the one in the cache
+                // do conditional get.
+                EntityTagHeaderValue actualEtag = null;
+                if (etags.Count > 0 && ETagHandler.ETagCache.TryGetValue(resource, out actualEtag))
+                {
+                    if (etags.Any(etag => etag.Tag == actualEtag.Tag))
+                    {
+                        return NotModifiedResponse(cancellationToken);
+                    }
+                }
+            }
+            else if (request.Method == HttpMethod.Put)
+            {
+                // should we ignore trailing slash
+                var resource = request.RequestUri.ToString();
+
+                ICollection<EntityTagHeaderValue> etags = request.Headers.IfMatch;
+                // compare the Etag with the one in the cache
+                // do conditional get.
+
+                EntityTagHeaderValue actualEtag = null;
+                if (etags.Count > 0 && ETagHandler.ETagCache.TryGetValue(resource, out actualEtag))
+                {
+                    var matchFound = etags.Any(etag => etag.Tag == actualEtag.Tag);
+
+                    if (!matchFound)
+                    {
+                        return ConflictResponse(cancellationToken);
+                    }
+                }
+            }
+            return base.SendAsync(request, cancellationToken).ContinueWith(task =>
+            {
+                var httpResponse = task.Result;
+                var eTagKey = request.RequestUri.ToString();
+                EntityTagHeaderValue eTagValue;
+
+                // Post would invalidate the collection, put should invalidate the individual item
+                if (!ETagCache.TryGetValue(eTagKey, out eTagValue) || request.Method == HttpMethod.Put || request.Method == HttpMethod.Post)
+                {
+                    eTagValue = new EntityTagHeaderValue("\"" + Guid.NewGuid().ToString() + "\"");
+                    ETagCache.AddOrUpdate(eTagKey, eTagValue, (key, existingVal) => eTagValue);
+                }
+                httpResponse.Headers.ETag = eTagValue;
+
+                return httpResponse;
+            });
+        }
+
+        private static Task<HttpResponseMessage> NotModifiedResponse(CancellationToken cancellationToken)
+        {
+            var response = new NotModifiedResponse { Content = new StringContent("The resource is not modified") };
+
+            return Task.Factory.StartNew<HttpResponseMessage>(task => response, cancellationToken);
+        }
+
+        private static Task<HttpResponseMessage> ConflictResponse(CancellationToken cancellationToken)
+        {
+            var response = new ConflictResponse { Content = new StringContent("If-Match header value is different from the ETag") };
+
+            return Task.Factory.StartNew<HttpResponseMessage>(task => response, cancellationToken);
+        }
+    }
+}

src/WebApiContrib/ResponseMessages/ConflictResponse.cs

@@ -0,0 +1,27 @@
+using System.Net;
+using System.Net.Http;
+
+namespace WebApiContrib.ResponseMessages
+{
+    public class ConflictResponse : ResourceResponseBase
+    {
+        public ConflictResponse() : base(HttpStatusCode.Conflict)
+        {
+        }
+
+        public ConflictResponse(IApiResource apiResource) : base(HttpStatusCode.Conflict, apiResource)
+        {
+        }
+    }
+
+    public class ConflictResponse<T> : HttpResponseMessage<T>
+    {
+        public ConflictResponse() : base(HttpStatusCode.Conflict)
+        {
+        }
+
+        public ConflictResponse(T resource) : base(resource, HttpStatusCode.Conflict)
+        {
+        }
+    }
+}

src/WebApiContrib/WebApiContrib.csproj

@@ -66,7 +66,7 @@
   </ItemGroup>
   <ItemGroup>
     <Compile Include="Formatting\JsonpFormatter.cs" />
-    <Compile Include="Internal\MediaTypeConstants.cs" />    
+    <Compile Include="Internal\MediaTypeConstants.cs" />
     <Compile Include="Conneg\ContentNegotiation.cs" />
     <Compile Include="Content\CompressedContent.cs" />
     <Compile Include="Content\SimpleObjectContent.cs" />
@@ -77,19 +77,21 @@
     <Compile Include="Internal\Extensions\EnumerableExtensions.cs" />
     <Compile Include="Internal\ReflectionHelper.cs" />
     <Compile Include="MessageHandlers\EncodingHandler.cs" />
+    <Compile Include="MessageHandlers\ETagHandler.cs" />
     <Compile Include="MessageHandlers\LoggingHandler.cs" />
     <Compile Include="MessageHandlers\MethodOverrideHandler.cs" />
-    <Compile Include="MessageHandlers\NotAcceptableMessageHandler.cs" />    
+    <Compile Include="MessageHandlers\NotAcceptableMessageHandler.cs" />
     <Compile Include="MessageHandlers\SimpleCorsHandler.cs" />
     <Compile Include="MessageHandlers\UriExtensionMappings.cs" />
     <Compile Include="MessageHandlers\UriFormatExtensionHandler.cs" />
-    <Compile Include="Messages\ApiLoggingInfo.cs" />        
+    <Compile Include="Messages\ApiLoggingInfo.cs" />
     <Compile Include="MessageHandlers\HeadMessageHandler.cs" />
-    <Compile Include="MessageHandlers\HttpMethodTunnelMessageHandler.cs" />    
+    <Compile Include="MessageHandlers\HttpMethodTunnelMessageHandler.cs" />
     <Compile Include="MessageHandlers\SelfHostConsoleOutputHandler.cs" />
     <Compile Include="MessageHandlers\TraceMessageHandler.cs" />
     <Compile Include="MessageHandlers\UriFormatExtensionMessageHandler.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
+    <Compile Include="ResponseMessages\ConflictResponse.cs" />
     <Compile Include="ResponseMessages\CreateResponse.cs" />
     <Compile Include="ResponseMessages\MovedPermanentlyResponse.cs" />
     <Compile Include="ResponseMessages\OkResponse.cs" />

test/WebApiContribTests/MessageHandlers/ETagHandlerTests.cs

@@ -0,0 +1,88 @@
+using System;
+using System.Collections.Generic;
+using System.Net;
+using System.Net.Http;
+using System.Net.Http.Headers;
+using NUnit.Framework;
+using Should;
+using WebApiContrib.MessageHandlers;
+
+namespace WebApiContribTests.MessageHandlers
+{
+    [TestFixture]
+    public class ETagHandlerTests : MessageHandlerTester
+    {
+        private KeyValuePair<string, EntityTagHeaderValue> etag = new KeyValuePair<string, EntityTagHeaderValue>("foo/bar", new EntityTagHeaderValue("\"" + Guid.NewGuid() + "\""));
+
+        [Test]
+        public void Should_return_NotModified_if_ETag_is_found_in_the_cache()
+        {
+            var eTagHandler = GetHandler();
+
+            var requestMessage = new HttpRequestMessage(HttpMethod.Get, etag.Key);
+            requestMessage.Headers.Add("If-None-Match", etag.Value.Tag);
+            AddETagValue(etag);
+            var response = ExecuteRequest(eTagHandler, requestMessage);
+
+            response.StatusCode.ShouldEqual(HttpStatusCode.NotModified);
+        }
+
+        [Test]
+        public void Should_return_Conflict_for_Put_if_key_is_in_header_but_match_not_found_in_cache()
+        {
+            var eTagHandler = GetHandler();
+
+            var requestMessage = new HttpRequestMessage(HttpMethod.Put, etag.Key);
+            requestMessage.Headers.Add("If-Match", etag.Value.Tag);
+
+            var newRandomValue = new EntityTagHeaderValue("\"" + Guid.NewGuid() + "\"");
+            AddETagValue(new KeyValuePair<string, EntityTagHeaderValue>(etag.Key, newRandomValue));
+
+            var response = ExecuteRequest(eTagHandler, requestMessage);
+
+            response.StatusCode.ShouldEqual(HttpStatusCode.Conflict);
+        }
+
+        [Test]
+        public void Post_should_return_OK_and_ETag_in_Header_and_update_Cache_if_ETag_is_found_in_the_cache()
+        {
+            var eTagHandler = GetHandler();
+
+            var requestMessage = new HttpRequestMessage(HttpMethod.Post, "foo/bar");
+            requestMessage.Headers.Add("If-None-Match", etag.Value.Tag);
+            AddETagValue(etag);
+            ETagHandler.ETagCache.Count.ShouldEqual(1);
+            var response = ExecuteRequest(eTagHandler, requestMessage);
+
+            response.StatusCode.ShouldEqual(HttpStatusCode.OK);
+            response.Headers.ETag.ShouldNotBeNull();
+            ETagHandler.ETagCache.Count.ShouldEqual(1);
+        }
+
+        [Test]
+        public void Get_should_return_OK_and_ETag_in_Header_and_add_to_Cache_if_ETag_is_not_found_in_the_cache()
+        {
+            var eTagHandler = GetHandler();
+
+            var requestMessage = new HttpRequestMessage(HttpMethod.Get, "foo/bar");
+            requestMessage.Headers.Add("If-None-Match", etag.Value.Tag);
+            // not added to cache
+            ETagHandler.ETagCache.Count.ShouldEqual(0);
+            var response = ExecuteRequest(eTagHandler, requestMessage);
+
+            response.StatusCode.ShouldEqual(HttpStatusCode.OK);
+            response.Headers.ETag.ShouldNotBeNull();
+            ETagHandler.ETagCache.Count.ShouldEqual(1);
+        }
+
+        private static void AddETagValue(KeyValuePair<string, EntityTagHeaderValue> pair)
+        {
+            ETagHandler.ETagCache.AddOrUpdate(pair.Key, pair.Value, (key, val) => pair.Value);
+        }
+
+        private ETagHandler GetHandler()
+        {
+            return new ETagHandler();
+        }
+    }
+}

test/WebApiContribTests/MessageHandlers/MessageHandlerTester.cs

@@ -22,9 +22,7 @@ public HttpResponseMessage ExecuteRequest(DelegatingHandler testTarget, HttpRequ
 
                 var requestTask = SendAsync(requestMessage, new CancellationToken());
 
-                while (!requestTask.IsCompleted)
-                {
-                }
+                requestTask.Wait(5000); // 5 second timeout - tests should be quicker than this, but better than infinite for now
 
                 return requestTask.Result;
             }

test/WebApiContribTests/ResponseMessages/ConflictResponseMessageTests.cs

@@ -0,0 +1,45 @@
+using System.Net;
+using NUnit.Framework;
+using Should;
+using WebApiContrib.ResponseMessages;
+
+namespace WebApiContribTests.ResponseMessages
+{
+    [TestFixture]
+    public class ConflictResponseMessageTests : HttpResponseMessageTester
+    {
+        [Test]
+        public void Should_return_an_http_response_message_with_expected_status()
+        {
+            var response = new ConflictResponse();
+
+            AssertExpectedStatus(response);
+        }
+
+        [Test]
+        public void Should_add_location_header_to_the_message_when_response_contains_a_api_resource()
+        {
+            var apiResource = new TestResource();
+
+            var response = new ConflictResponse(apiResource);
+            AssertExpectedStatus(response);
+            response.Headers.Location.ShouldEqual(apiResource.Location);
+        }
+
+        [Test]
+        public void Should_add_content_to_message_when_its_a_typed_response_message()
+        {
+            var apiResource = new TestResource();
+            var response = new ConflictResponse<TestResource>(apiResource);
+            AssertExpectedStatus(response);
+            response.Headers.Location.ShouldEqual(apiResource.Location);
+            response.Content.ShouldNotBeNull();
+            response.Content.ObjectType.ShouldEqual(typeof(TestResource));
+        }
+
+        protected override HttpStatusCode? ExpectedStatusCode
+        {
+            get { return HttpStatusCode.Conflict; }
+        }
+    }
+}

test/WebApiContribTests/WebApiContribTests.csproj

@@ -88,10 +88,12 @@
     <Compile Include="Helpers\PrecannedMessageHandler.cs" />
     <Compile Include="IoC\DependencyInjectionTests.cs" />
     <Compile Include="MessageHandlers\EncodingHandlerTests.cs" />
+    <Compile Include="MessageHandlers\ETagHandlerTests.cs" />
     <Compile Include="MessageHandlers\HeadMessageHandlerTests.cs" />
     <Compile Include="MessageHandlers\LoggingHandlerTests.cs" />
     <Compile Include="MessageHandlers\MessageHandlerTester.cs" />
     <Compile Include="MessageHandlers\NotAcceptableMessageHandlerTests.cs" />
+    <Compile Include="ResponseMessages\ConflictResponseMessageTests.cs" />
     <Compile Include="ResponseMessages\CreateResponseMessageTests.cs" />
     <Compile Include="ResponseMessages\HttpResponseMessageTester.cs" />
     <Compile Include="ResponseMessages\NotModifiedResponseTests.cs" />